Liquid modified PET polyesters for lithographic inks

Abstract

The present invention is directed to a method of making liquid polyester resins, and the liquid polyester resins produced by the method. The liquid polyester resins are prepared by depolymerizing virgin, scrap, recycled or reclaimed polyethylene terephthalate (PET) via an alcoholysis reaction with one or more mono-alcohols and/or polyols; transesterifying the resulting polyol oligomer with vegetable oils or fatty acid alkyl esters; and re-polymerizing with acids or anhydrides. The present invention also provides ink and coating compositions, and overprint varnishes, comprising the liquid polyester resins of the invention.

What is claimed is: 
     
       1. A method of making a liquid polyester resin comprising the steps of:
 a) depolymerizing virgin, scrap, recycled and/or reclaimed polyethylene terephthalate (PET) via an alcoholysis reaction with one or more mono-alcohols and/or polyols; 
 b) transesterifying the resulting polyol oligomer of step a) with one or more vegetable oils, fatty acid alkyl esters, or oil-modified alkyd resins; and 
 c) re-polymerizing the oil-modified polyol oligomer of step b) via reaction with one or more acids or anhydrides, wherein the acids or anhydrides are present in an amount of 5 wt % to 30 wt %, based on the total weight of all components; 
 wherein the weight ratio of the PET to the total of all mono-alcohols and polyols used in step a) is in a range from 20:1 to 10:1; to obtain a liquid polyester resin wherein the acid value of the liquid polyester resin is 5 to 50 mg KOH/g; the liquid polyester resin has one or both of a number average molecular weight of 800 to 5000 Daltons, and a weight average molecular weight of 1500 to 10,000 Daltons; the liquid polyester resin is soluble in toluene, aromatic and aliphatic mineral oils, vegetable oils, fatty acid alkyl esters, and triglycerides; and wherein the liquid polyester resin is suitable for use in lithographic inks. 
 
     
     
       2. The method of  claim 1 , wherein a fatty acid methylester is used in step b). 
     
     
       3. The method of  claim 1 , wherein the one or more acids or anhydrides are each independently selected from the group consisting of mono-, di-, or tricarboxylic acid derivatives. 
     
     
       4. The method of  claim 1 , wherein the components are used in an amount of:
 a) 50 wt % to 60 wt % PET, based on the total weight of all components; 
 b) 5 wt % to 25 wt % one or more mono-alcohols and/or polyols, based on the total weight of all components; 
 c) 25 wt % to 60 wt % one or more vegetable oils, fatty acid alkyl esters, or oil-modified alkyd resins, based on the total weight of all components; and 
 d) 5 wt % to 30 wt % one or more acids or acid anhydrides, based on the total weight of all components. 
 
     
     
       5. The method of  claim 1 , wherein the hydroxyl value of the liquid polyester resin is less than 100 mg KOH/g. 
     
     
       6. The method of  claim 1 , wherein the acid value of the liquid polyester resin is 31 to 50 mg KOH/g.